The basic operation in the processing of silver halide color photographic materials (referred to hereinafter as color photosensitive materials), in general, consists of a color development process and a desilvering process. In the color development process, the exposed silver halide is reduced by a color developing agent to form silver and at the same time the oxidized color developing agent reacts with a color forming agent (a coupler) and provides a dye image. Then, in the subsequent desilvering process, the silver which has been produced in the color development process is oxidized by the action of an oxidizing agent which is commonly called a bleaching agent and then dissolved by means of a complex silver ion forming agent which is commonly called a fixing agent. Only the dye image is then left behind in the color photographic material as a result of passing through this desilvering process.
The desilvering process described above can consist of a procedure involving two baths, namely, a bleaching bath which contains a bleaching agent and a fixing bath which contains a fixing agent, a procedure involving a single bleach-fixing bath in which both bleaching agent and fixing agent are present, a procedure involving two baths consisting of a bleaching bath and a bleach-fixing bath, or a procedure involving three baths, namely, a bleaching bath, a bleach-fixing bath and a fixing bath, for example. Furthermore, each of these baths may in fact be comprised of a plurality of tanks.
Actual development processing includes various auxiliary operations as well as the basic operations indicated above for maintaining the photographic and physical quality of the image and for improving the storage properties of the image. For example, use is made of film hardening baths, stopping baths, image stabilizing baths and water washing baths.
Recent years have seen the widespread use of small in-store processing service systems known as mini-labs and there is a need for a shortening of the time required for processing as described above in order to meet the demand for rapid and reliable processing.
In particular, there has been a great demand for a shortening of the desilvering process which takes up the greater part of the processing time in conventional processing.
However, the ethylenediaminetetraacetic acid ferric complex salts which are used in the main as the bleaching agents which are used in bleaching baths and bleach-fixing baths have a fundamental weakness in that they have only a weak oxidizing power and, although improvements can be achieved with the conjoint use of various bleaching accelerators, they are unable to satisfy the aforementioned demands.
Furthermore, methods of processing in which the pH of the bleaching bath or bleach-fixing bath is reduced in order to increase the oxidizing power of the ethylenediaminetetraacetic acid ferric complex salts have been adopted, but in processing methods of this type color formation failure due to the formation of leuco cyan dyes, a phenomenon known as color restoration failure occurs.
On the other hand, ferricyanide, dichromates, ferric chloride, persulfate and bromates, for example, are all known as bleaching agents which have a strong oxidizing power, but these materials present many disadvantages from the viewpoints of environmental protection, safety in handling and metal corrosion, for example, and the situation is such that they cannot be widely used in in-store processing applications, for example.
Among these agents, bleaching baths having a pH of about 6 which contain 1,3-diaminopropanetetraacetic acid ferric complex salts which have a redox potential of at least 150 mV and a strong oxidizing power have been used, for example, in JP-A-62-222252 (the term "JP-A" as used herein refers to a "published unexamined Japanese patent application"), and it is possible to bleach silver more rapidly in this way than with bleaching baths which contain ethylenediaminetetraacetic acid ferric complex salts, but there is a disadvantage in that color fogging of a type known as bleaching fogs occurs if the bleaching process is carried out directly after color development without passing through an intermediate bath. Furthermore, bleaching baths containing 1,3-diaminopropanetetraacetic acid ferric complex salts (for example, at pH 5.0) have also been disclosed in JP-A-62-24253.
The above mentioned bleaching baths can be used in desilvering operations with two processing baths with a fixing bath or a processing bath which has a fixing ability, such as a bleach-fixing bath, following the bleaching bath.
Furthermore, methods of processing in bleaching baths having a low pH as disclosed in JP-A-1-206341 are known as a means of achieving rapid silver bleaching and overcoming the problem of bleach fogging, but color restoration failure inevitably occurs with this technique.
Processing with a color restoring bath having a high pH after the bleaching process as disclosed in JP-A-64-558 is known as a means of overcoming color restoration failure, but these methods are not compatible with rapid processing.
Furthermore, when processing is carried out in a bleaching bath which contains 1,3-propylenediaminetetraacetic acid ferric complex salt there is a definite problem with the considerable staining which occurs with the passage of time after processing as compared to the case of bleaching baths which contain ethylenediaminetetraacetic acid ferric complex salts.